Coal gangue is a type of rock waste product with dark gray color during coal mining and washing. The curing agent stabilizes soils by improving their physico-mechanical properties, allowing the soils to be reused in engineering as the subgrade fill. This study investigates the impact of SAHP curing agent on road performance parameters of coal gangue. The results showed that the road performance parameters of coal gangue increase with the curing agent content. The compressive resilience modulus of 7 days and California bearing ratio of coal gangue with 0.2% curing agent meet the specifications. The scanning electron microscope reveals the presence of agglomerated gels and hexagonal prism crystals between coal gangue particles. The observed crystals are ettringite, and the gels are silicate gel (nSiO2·mH2O) formed by the reaction of Na2O·nSiO2 with CO2 and H2O, as determined by combined X-ray diffraction and energy spectrum analysis. The improved coal gangue by the curing agent can be utilized as subgrade fill, supporting the reuse of coal gangue in highway engineering.Mine wastes are generated nearly in all mining operations. As the unwanted by-products of mining, they are often placed in large heaps on the mining sites. Inappropriate disposal of the mine wastes (coal gangue, tailings, and other wastes) would release hazardous substances, which exert great impact on the local ecological environment and human health [1, 2]. The oxidation of sulfide minerals is the main source of acid mine drainage (AMD), which results in the surface and groundwater contamination. As the typical sedimentary rock, coal contains a large amount of carbon, sulfur, and hydrogen elements. The oxidation of pyrite is the major source of AMD or coal mine drainage (CMD) in the coal industry [3]. During the complex oxidation process among water, air, and exposed coal rock, the heavy metals leach into the water gradually. A comprehensive evaluation of the quality of the soils, stream, and water bodies near the coal-washing waste dump from the geochemical perspective is necessary for water remediation plan [4]. It is worth noting that, not all CMD are hated, advanced technology makes it possible to reuse the mining wastes, such as recovering rare earth elements [3].Large size of the mining industry determines the deposition of coal gangue, which occupies a large area of land resources [2, 5]. Oxidation and spontaneous combustion exist during the long-term coal gangue accumulation, and harmful gases such as SO2, NOx, and CO can also be released [1]. Coal gangue has been utilized in the preparation of cement [6], powder asphalt mortar [7], and autoclaved aerated concrete [8]. With the rapid development of transportation infrastructure construction, coal gangue was also proposed to be reused in highway engineering as the filling material.Coal gangue can satisfy the basic requirements for road engineering materials after being compacted or stabilized, which offers certain potential
{"title":"Study of Road Performance and Curing Mechanism of Coal Gangue by Curing Agent","authors":"Zhe Ren, Rui Zhang, Jian Zhang, Qiang Gao, Chuanxiao Liu, Yingying Wan, Jianjun Liu, Qingliang Hu, Chengbin Ren","doi":"10.2113/2024/lithosphere_2023_183","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_183","url":null,"abstract":"Coal gangue is a type of rock waste product with dark gray color during coal mining and washing. The curing agent stabilizes soils by improving their physico-mechanical properties, allowing the soils to be reused in engineering as the subgrade fill. This study investigates the impact of SAHP curing agent on road performance parameters of coal gangue. The results showed that the road performance parameters of coal gangue increase with the curing agent content. The compressive resilience modulus of 7 days and California bearing ratio of coal gangue with 0.2% curing agent meet the specifications. The scanning electron microscope reveals the presence of agglomerated gels and hexagonal prism crystals between coal gangue particles. The observed crystals are ettringite, and the gels are silicate gel (nSiO2·mH2O) formed by the reaction of Na2O·nSiO2 with CO2 and H2O, as determined by combined X-ray diffraction and energy spectrum analysis. The improved coal gangue by the curing agent can be utilized as subgrade fill, supporting the reuse of coal gangue in highway engineering.Mine wastes are generated nearly in all mining operations. As the unwanted by-products of mining, they are often placed in large heaps on the mining sites. Inappropriate disposal of the mine wastes (coal gangue, tailings, and other wastes) would release hazardous substances, which exert great impact on the local ecological environment and human health [1, 2]. The oxidation of sulfide minerals is the main source of acid mine drainage (AMD), which results in the surface and groundwater contamination. As the typical sedimentary rock, coal contains a large amount of carbon, sulfur, and hydrogen elements. The oxidation of pyrite is the major source of AMD or coal mine drainage (CMD) in the coal industry [3]. During the complex oxidation process among water, air, and exposed coal rock, the heavy metals leach into the water gradually. A comprehensive evaluation of the quality of the soils, stream, and water bodies near the coal-washing waste dump from the geochemical perspective is necessary for water remediation plan [4]. It is worth noting that, not all CMD are hated, advanced technology makes it possible to reuse the mining wastes, such as recovering rare earth elements [3].Large size of the mining industry determines the deposition of coal gangue, which occupies a large area of land resources [2, 5]. Oxidation and spontaneous combustion exist during the long-term coal gangue accumulation, and harmful gases such as SO2, NOx, and CO can also be released [1]. Coal gangue has been utilized in the preparation of cement [6], powder asphalt mortar [7], and autoclaved aerated concrete [8]. With the rapid development of transportation infrastructure construction, coal gangue was also proposed to be reused in highway engineering as the filling material.Coal gangue can satisfy the basic requirements for road engineering materials after being compacted or stabilized, which offers certain potential ","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"12 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140072422","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-12DOI: 10.2113/2024/lithosphere_2023_341
Yaohui Liu, Fang Lv, Zebin Ouyang, Tao Wang
Grouting is an effective method to solve the problem of water inrush in tunnel and underground engineering. However, rock fractures are often simplified as horizontal and smooth fractures in most grouting studies, while studies on vertical inclined fractures are still rare. To investigate the diffusion law in vertical inclined fractures, a vertical inclined fracture grouting simulation device was developed. A new type of cement slurry with low weight and high flowing water resistance was developed by combining carbon nanotube (CNT) slurry with foamed cement. Physical simulation experiments were conducted to investigate various factors (initial flowing water, inclination angle, sand content, and grouting rate) on the sealing efficiency of grouting. Results show that the high foam content has a negative effect on the compressive strength of the slurry, and has a positive effect on the fluidity and water resistance. The optimum ratio of slurry is 30% foam content, 1.0% CNT content, 1.3 water/cement ratio, and 3% additive content. The inclination angle and inclination direction of the fracture have a great influence on the sealing efficiency of grouting. Foam-CNT composite grouts can meet the requirement of flowing water grouting in vertical inclined fractures.Water inrush is a common problem in tunneling and underground engineering. Water inrush will delay the project and result in high personal injury and property damage [1, 2]. Grouting is an effective method to solve the problem of water inrush [3]. Grouting can improve the strength and reduce the permeability of the rock by injecting slurry into the rock fractures [4-7]. Considerable progress has been made in the area of flowing water grouting in recent years [8-10]. However, the theory of grouting still cannot meet the requirements of practical engineering.Many scholars studied the sealing and diffusion law of flowing water grouting [11-14]. Sui et al. [15] investigated the effects of fracture width, initial flowing rate, grouting time, and grouting amount on the sealing efficiency of flowing water grouting through laboratory simulation experiments. Liang et al. [16] demonstrated that the inclination of fracture has a significant effect on the sealing efficiency and the diffusion law of flowing water grouting. Depending on the relation between the direction of flowing water and fracture, rock fractures can be divided into horizontal fractures, horizontally inclined fractures, and vertically inclined fractures (Figure 1). However, in most studies on flowing water grouting, rock fractures are simplified as horizontal fractures [17, 18], and studies on the vertical inclined fracture grouting are still rare.Many scholars have proved that the diffusion law of liquid in inclined fractures and horizontal fractures is completely different [19]. Graf et al. [20] proposed a numerical method to discretize inclined nonplanar two-dimensional (2D) fractures within a three-dimensional (3D) finite element grid
{"title":"Experimental Investigation on the Grouting Performance of Foam-CNT Composite Grouts in Vertical Inclined Fractures Under Flowing Condition","authors":"Yaohui Liu, Fang Lv, Zebin Ouyang, Tao Wang","doi":"10.2113/2024/lithosphere_2023_341","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_341","url":null,"abstract":"Grouting is an effective method to solve the problem of water inrush in tunnel and underground engineering. However, rock fractures are often simplified as horizontal and smooth fractures in most grouting studies, while studies on vertical inclined fractures are still rare. To investigate the diffusion law in vertical inclined fractures, a vertical inclined fracture grouting simulation device was developed. A new type of cement slurry with low weight and high flowing water resistance was developed by combining carbon nanotube (CNT) slurry with foamed cement. Physical simulation experiments were conducted to investigate various factors (initial flowing water, inclination angle, sand content, and grouting rate) on the sealing efficiency of grouting. Results show that the high foam content has a negative effect on the compressive strength of the slurry, and has a positive effect on the fluidity and water resistance. The optimum ratio of slurry is 30% foam content, 1.0% CNT content, 1.3 water/cement ratio, and 3% additive content. The inclination angle and inclination direction of the fracture have a great influence on the sealing efficiency of grouting. Foam-CNT composite grouts can meet the requirement of flowing water grouting in vertical inclined fractures.Water inrush is a common problem in tunneling and underground engineering. Water inrush will delay the project and result in high personal injury and property damage [1, 2]. Grouting is an effective method to solve the problem of water inrush [3]. Grouting can improve the strength and reduce the permeability of the rock by injecting slurry into the rock fractures [4-7]. Considerable progress has been made in the area of flowing water grouting in recent years [8-10]. However, the theory of grouting still cannot meet the requirements of practical engineering.Many scholars studied the sealing and diffusion law of flowing water grouting [11-14]. Sui et al. [15] investigated the effects of fracture width, initial flowing rate, grouting time, and grouting amount on the sealing efficiency of flowing water grouting through laboratory simulation experiments. Liang et al. [16] demonstrated that the inclination of fracture has a significant effect on the sealing efficiency and the diffusion law of flowing water grouting. Depending on the relation between the direction of flowing water and fracture, rock fractures can be divided into horizontal fractures, horizontally inclined fractures, and vertically inclined fractures (Figure 1). However, in most studies on flowing water grouting, rock fractures are simplified as horizontal fractures [17, 18], and studies on the vertical inclined fracture grouting are still rare.Many scholars have proved that the diffusion law of liquid in inclined fractures and horizontal fractures is completely different [19]. Graf et al. [20] proposed a numerical method to discretize inclined nonplanar two-dimensional (2D) fractures within a three-dimensional (3D) finite element grid","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"18 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140301026","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-12DOI: 10.2113/2024/lithosphere_2023_344
Qian Yuan
The concept that lithosphere detachment or break-off has long been conceived as a viable mechanism to explain prominent geological phenomena in Earth’s crust and the surface. One of the strengths of slab delamination mechanism is that it can account for the extensive magmatism in active orogenic belts due to the upwelling of the asthenosphere after the slab break-off. However, in the last 20 years, geodynamic simulations show that the inflow of the asthenosphere upon slab break-off is insufficient to cause significant melting of the overriding lithosphere adjacent to the slab window. The primary reasons include the occurrence of slab break-off at a location that is too deep to effectively heat the overriding lithospheric mantle. Another factor is the presence of a thin film of crustal material that is retained during the slab break- off, inhibiting a significant thermal perturbation within the lithosphere. In this work, we couple petrological–thermomechanical simulations with magmatic melting processes to examine the lithospheric melting and surface lithological expression associated with slab break-off. Our work shows that in the early Earth when the mantle temperature is relatively higher, shallow slab break-off can give rise to significant lithospheric melting during the development of slab break-off. Moreover, because the slab becomes weaker in the earlier hotter mantle, it may break-off prior to the stage of continental collision, thus the magmatism it induced may not give a direct constraint on the time of continental collision. Our study has implications for the interpretation of geological and tomography studies in orogenic belts. It also provides insights into reconciling conflicts between geodynamic and geological studies regarding slab break off-induced melting and magmatism.One of the most peculiar lithologies in Earth’s middle age is Proterozoic massif-type anorthosites (PMAs), a plutonic batholith-forming rock type temporally restricted to the Proterozoic [1-4]. Formally, PMAs are composed of at least 90% plagioclase feldspar accompanied by minor mafic silicates and Fe-Ti oxides [5]. PMAs are areally and volumetrically extensive, with the largest PMA being the Kunene Complex in SW Angola, which covers an area of 18,000 km2 [6]. A consensus has been largely reached on the mechanism by which anorthosites were concentrated. They formed through the accumulation of magmatic plagioclase at the top of a magma chamber due to the low density of plagioclase compared to coexisting melt [7]. However, despite their simple mineralogy and have been studied for over a century, the geodynamic setting accounting for PMAs remains hotly debated [1, 2, 8, 9].A variety of tectonic settings have been proposed for PMAs, including Andean-type continental arc, post-orogenic, anorogenic, and continental rift settings [2, 4, 10, 11]. In recent years, a new tectonic regime—slab break-off—has been adopted accounting for the origin of several PMAs in Asia based o
{"title":"Numerical Modeling of Melting Processes During Slab Break-off: Insights Into Tectonic Setting for Massif-Type Anorthosites","authors":"Qian Yuan","doi":"10.2113/2024/lithosphere_2023_344","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_344","url":null,"abstract":"The concept that lithosphere detachment or break-off has long been conceived as a viable mechanism to explain prominent geological phenomena in Earth’s crust and the surface. One of the strengths of slab delamination mechanism is that it can account for the extensive magmatism in active orogenic belts due to the upwelling of the asthenosphere after the slab break-off. However, in the last 20 years, geodynamic simulations show that the inflow of the asthenosphere upon slab break-off is insufficient to cause significant melting of the overriding lithosphere adjacent to the slab window. The primary reasons include the occurrence of slab break-off at a location that is too deep to effectively heat the overriding lithospheric mantle. Another factor is the presence of a thin film of crustal material that is retained during the slab break- off, inhibiting a significant thermal perturbation within the lithosphere. In this work, we couple petrological–thermomechanical simulations with magmatic melting processes to examine the lithospheric melting and surface lithological expression associated with slab break-off. Our work shows that in the early Earth when the mantle temperature is relatively higher, shallow slab break-off can give rise to significant lithospheric melting during the development of slab break-off. Moreover, because the slab becomes weaker in the earlier hotter mantle, it may break-off prior to the stage of continental collision, thus the magmatism it induced may not give a direct constraint on the time of continental collision. Our study has implications for the interpretation of geological and tomography studies in orogenic belts. It also provides insights into reconciling conflicts between geodynamic and geological studies regarding slab break off-induced melting and magmatism.One of the most peculiar lithologies in Earth’s middle age is Proterozoic massif-type anorthosites (PMAs), a plutonic batholith-forming rock type temporally restricted to the Proterozoic [1-4]. Formally, PMAs are composed of at least 90% plagioclase feldspar accompanied by minor mafic silicates and Fe-Ti oxides [5]. PMAs are areally and volumetrically extensive, with the largest PMA being the Kunene Complex in SW Angola, which covers an area of 18,000 km2 [6]. A consensus has been largely reached on the mechanism by which anorthosites were concentrated. They formed through the accumulation of magmatic plagioclase at the top of a magma chamber due to the low density of plagioclase compared to coexisting melt [7]. However, despite their simple mineralogy and have been studied for over a century, the geodynamic setting accounting for PMAs remains hotly debated [1, 2, 8, 9].A variety of tectonic settings have been proposed for PMAs, including Andean-type continental arc, post-orogenic, anorogenic, and continental rift settings [2, 4, 10, 11]. In recent years, a new tectonic regime—slab break-off—has been adopted accounting for the origin of several PMAs in Asia based o","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"21 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140313461","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rock joints are susceptible to slip instability due to dynamic load disturbances such as blasting, earthquakes, and fracturation. A series of direct shear tests under the dynamic load were conducted on sandstone plane joints using the RDS-200xl. The work investigated the effects of normal static loads and normal dynamic-load frequencies and amplitudes on plane joints. Besides, the following items were proposed, that is, the peak-to-valley response rate, shear velocity vibration dominant frequency, shear-stress reduction coefficient, and discrete element numerical simulation method for plane-joint direct shear tests. The results were as follows: (1) The normal dynamic load frequency played a role in attenuating the shear stress amplitude with a threshold value of 0.5 Hz. (2) The shear velocity of the plane joint was completely controlled by the high normal dynamic load frequency. Their vibrational dominant frequencies were identical. (3) The amplitude of shear stress increased, and the median stress decreased with the increased normal dynamic load amplitude. The reduction-coefficient equation for sandstone plane joints was proposed to evaluate the shear stress under the normal dynamic load disturbance. (4) The shear-stress hysteresis phenomenon existed in the plane joints under the normal dynamic load, which required excessive shear displacements to reach peak shear strength. The peak shear displacement increased with the increased normal static load. Numerical simulations and indoor tests showed that high- and low-shear-velocity regions were the main reason for shear-stress hysteresis. The findings are conducive to revealing the shear destabilization mechanism of rock joints under dynamic load disturbance.Rock is a complex geological body composed of joints and rock masses, and shear damage along the joints is one of the main damage modes of rocks [1]. The shear behavior of rock joints is an important basis for the project design and safety assessment in practical engineering. The force form of rock engineering is a combination of dynamic and static loads due to blasting, explosion, or seismic stimulation. Compared with static-load shear damage, the shear behavior of rocks under the dynamic load is more complicated. Research findings indicate that fault slip exhibits an inherent instability, characterized by a concurrent misalignment and a decline in the stress. When an earthquake occurs, normal and shear stresses change around the fault [2-4]. Therefore, it is of great significance to study the shear behavior of rock joints under the dynamic–static load combination.Tests consider real stresses in rock engineering, and research generally focuses on dynamic loading conditions in rocks’ normal and tangential directions. Guo et al. [5] investigated the fatigue damage and irreversible deformation of salt rocks under the uniaxial cyclic loading. The fatigue life of salt rocks is mainly affected by their structure and normal stress amplitude. Liu et al
{"title":"Study on Shear Slip Characteristics of Sandstone Plane Joints under Normal Dynamic Load Disturbance","authors":"Kangyu Wang, Caiping Lu, Yang Liu, Caijun Shao, Jian Zhou, Zhaowei Zhan","doi":"10.2113/2024/lithosphere_2023_282","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_282","url":null,"abstract":"Rock joints are susceptible to slip instability due to dynamic load disturbances such as blasting, earthquakes, and fracturation. A series of direct shear tests under the dynamic load were conducted on sandstone plane joints using the RDS-200xl. The work investigated the effects of normal static loads and normal dynamic-load frequencies and amplitudes on plane joints. Besides, the following items were proposed, that is, the peak-to-valley response rate, shear velocity vibration dominant frequency, shear-stress reduction coefficient, and discrete element numerical simulation method for plane-joint direct shear tests. The results were as follows: (1) The normal dynamic load frequency played a role in attenuating the shear stress amplitude with a threshold value of 0.5 Hz. (2) The shear velocity of the plane joint was completely controlled by the high normal dynamic load frequency. Their vibrational dominant frequencies were identical. (3) The amplitude of shear stress increased, and the median stress decreased with the increased normal dynamic load amplitude. The reduction-coefficient equation for sandstone plane joints was proposed to evaluate the shear stress under the normal dynamic load disturbance. (4) The shear-stress hysteresis phenomenon existed in the plane joints under the normal dynamic load, which required excessive shear displacements to reach peak shear strength. The peak shear displacement increased with the increased normal static load. Numerical simulations and indoor tests showed that high- and low-shear-velocity regions were the main reason for shear-stress hysteresis. The findings are conducive to revealing the shear destabilization mechanism of rock joints under dynamic load disturbance.Rock is a complex geological body composed of joints and rock masses, and shear damage along the joints is one of the main damage modes of rocks [1]. The shear behavior of rock joints is an important basis for the project design and safety assessment in practical engineering. The force form of rock engineering is a combination of dynamic and static loads due to blasting, explosion, or seismic stimulation. Compared with static-load shear damage, the shear behavior of rocks under the dynamic load is more complicated. Research findings indicate that fault slip exhibits an inherent instability, characterized by a concurrent misalignment and a decline in the stress. When an earthquake occurs, normal and shear stresses change around the fault [2-4]. Therefore, it is of great significance to study the shear behavior of rock joints under the dynamic–static load combination.Tests consider real stresses in rock engineering, and research generally focuses on dynamic loading conditions in rocks’ normal and tangential directions. Guo et al. [5] investigated the fatigue damage and irreversible deformation of salt rocks under the uniaxial cyclic loading. The fatigue life of salt rocks is mainly affected by their structure and normal stress amplitude. Liu et al","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"166 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139923763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-12DOI: 10.2113/2024/lithosphere_2023_283
Daniel Patias, Renjie Zhou, Jonathan C. Aitchison
New whole-rock major and trace element geochemical, zircon U-Pb geochronological, and Hf isotopic data from gabbroic rocks in New Zealand’s mid-Permian Dun Mountain ophiolite belt (DMO) provide insight into the evolution of subduction systems and early stages of intraoceanic arc development. Fe-oxide-bearing gabbros yielded high εHf(t) values (+10.3 to +13) and zircon U-Pb ages of 271.6 ± 0.6 Ma. In contrast, Fe-Ti-oxide-bearing gabbros of 268.1 ± 0.6 Ma show more enriched geochemical characteristics, including a wide range of εHf(t) values (+15.5 to +6.8). New findings strengthen the evolutionary model for the DMO and place constraints on its youngest known magmatic episode. We infer that late magmatism fingerprinted by these gabbros, including consistent negative Nb-Ta anomalies, reflects early stages of arc development and formation of island arc tholeiites on the DMO. Our model is consistent with other existing regional geochronological and geochemical data, implying that the DMO had an early stage of normal-mid-ocean ridge basalt crustal accretion followed by an influx of slab-derived components and maturity of the subducting system between ca. 271.6 and 268 Ma. These results extend our understanding of the evolution of distinct intraoceanic systems.Ophiolites are fragments of ancient oceanic lithosphere that have been incorporated into continental margins [1, 2]. They can be formed in distinct tectonic settings, including mid-ocean ridge, back-arc, and forearc [3, 4]. However, since the recognition of lava with island arc tholeiites (IAT) and calc-alkaline geochemical signatures in the Troodos ophiolite [5], a growing number of studies have associated these fragments of ancient oceanic lithosphere to intraoceanic convergent plate margins [6]. Such ophiolites, formed during sea-floor spreading above the subducting slab, are referred to as suprasubduction zone (SSZ) ophiolites [7]. They are widely interpreted to form during subduction initiation and early growth of island arcs [2, 7, 8]. As a result, studying their geochemical and geochronological signatures is crucial for understanding plate tectonic processes and intraoceanic systems [3, 9-12].Different geochemical signatures, such as forearc basalt (FAB), boninite, and IAT, can often be found in rocks from the ophiolitic crustal section. These signatures are widely used to identify different stages of the ophiolite and the evolution of the intraoceanic system [13, 14]. However, diverse processes can affect the geochemical characteristics of ophiolitic rocks, for example, the injection of fluids and melts from the slab [15, 16], distinct episodes of melt extraction from the mantle [17], and cumulate processes [18, 19]. Additionally, specific processes, such as colder, denser slabs descending more quickly or a thicker sedimentary cover of the slab, can also contribute to the geochemical heterogeneity of ophiolitic rocks [20-22]. This complexity can make it challenging to determine an ophioli
{"title":"Geochronological and Geochemical Constraints on the Magmatic Evolution of the Dun Mountain Ophiolite Belt, New Zealand","authors":"Daniel Patias, Renjie Zhou, Jonathan C. Aitchison","doi":"10.2113/2024/lithosphere_2023_283","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_283","url":null,"abstract":"New whole-rock major and trace element geochemical, zircon U-Pb geochronological, and Hf isotopic data from gabbroic rocks in New Zealand’s mid-Permian Dun Mountain ophiolite belt (DMO) provide insight into the evolution of subduction systems and early stages of intraoceanic arc development. Fe-oxide-bearing gabbros yielded high εHf(t) values (+10.3 to +13) and zircon U-Pb ages of 271.6 ± 0.6 Ma. In contrast, Fe-Ti-oxide-bearing gabbros of 268.1 ± 0.6 Ma show more enriched geochemical characteristics, including a wide range of εHf(t) values (+15.5 to +6.8). New findings strengthen the evolutionary model for the DMO and place constraints on its youngest known magmatic episode. We infer that late magmatism fingerprinted by these gabbros, including consistent negative Nb-Ta anomalies, reflects early stages of arc development and formation of island arc tholeiites on the DMO. Our model is consistent with other existing regional geochronological and geochemical data, implying that the DMO had an early stage of normal-mid-ocean ridge basalt crustal accretion followed by an influx of slab-derived components and maturity of the subducting system between ca. 271.6 and 268 Ma. These results extend our understanding of the evolution of distinct intraoceanic systems.Ophiolites are fragments of ancient oceanic lithosphere that have been incorporated into continental margins [1, 2]. They can be formed in distinct tectonic settings, including mid-ocean ridge, back-arc, and forearc [3, 4]. However, since the recognition of lava with island arc tholeiites (IAT) and calc-alkaline geochemical signatures in the Troodos ophiolite [5], a growing number of studies have associated these fragments of ancient oceanic lithosphere to intraoceanic convergent plate margins [6]. Such ophiolites, formed during sea-floor spreading above the subducting slab, are referred to as suprasubduction zone (SSZ) ophiolites [7]. They are widely interpreted to form during subduction initiation and early growth of island arcs [2, 7, 8]. As a result, studying their geochemical and geochronological signatures is crucial for understanding plate tectonic processes and intraoceanic systems [3, 9-12].Different geochemical signatures, such as forearc basalt (FAB), boninite, and IAT, can often be found in rocks from the ophiolitic crustal section. These signatures are widely used to identify different stages of the ophiolite and the evolution of the intraoceanic system [13, 14]. However, diverse processes can affect the geochemical characteristics of ophiolitic rocks, for example, the injection of fluids and melts from the slab [15, 16], distinct episodes of melt extraction from the mantle [17], and cumulate processes [18, 19]. Additionally, specific processes, such as colder, denser slabs descending more quickly or a thicker sedimentary cover of the slab, can also contribute to the geochemical heterogeneity of ophiolitic rocks [20-22]. This complexity can make it challenging to determine an ophioli","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"5 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139501389","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Irum Irum, Humaad Ghani, Edward R. Sobel, Gerold Zeilinger, Uwe Altenberger
New middle Miocene to Pliocene (~14–3 Ma) apatite fission track (AFT) cooling ages combined with published K–Ar/Ar–Ar and zircon fission track (ZFT) ages from the Hazara and Swat regions of Pakistan are used to explain the Oligocene to Pliocene structural evolution in the Western Himalaya. The structural model explains the distribution of K–Ar/Ar–Ar ages in three distinct age groups (Proterozoic, Paleozoic-Mesozoic, and Eocene to Oligocene). The Proterozoic to Mesozoic sequence of northern Hazara and Swat experienced elevated temperature and pressure conditions, evident by reset Eocene to Oligocene K–Ar/Ar–Ar hornblende and Eocene to Miocene muscovite ages, caused by Kohistan overthrusting the Indian margin during and after the India–Asia collision. Samples from the Indus syntaxis with Paleo to Mesoproterozoic K–Ar/Ar–Ar hornblende ages and Eocene to Oligocene Ar–Ar muscovite ages show no signs of Cenozoic metamorphism; these samples were thermally imprinted up to the Ar–Ar muscovite closure temperature. Neoproterozoic to Lower Paleozoic rocks from the southern parts of Hazara and Swat show Mesozoic to Oligocene partially reset Ar–Ar muscovite ages and preservation of Ordovician metamorphism. The combined analysis of published K–Ar/Ar–Ar (muscovite), ZFT, and new AFT ages (~14–12 Ma) suggests that the Main Central thrust/Panjal thrust was active from Oligocene to early Miocene (~30–18 Ma), and the Nathia-Gali and Main Boundary thrusts were active from the middle to late Miocene (~14–9 Ma) in the Hazara area. New and published AFT ages (~6–3 Ma) from the Indus syntaxis suggest that early Pliocene tectonic thickening in the hinterland formed the N–S trending Indus anticline, creating an erosional half window in the Main Mantle thrust, forming the Indus syntaxis, and dividing the Main Central thrust sheet into the Hazara and Swat segments.The Himalaya, one of the most tectonically active mountain ranges in the world, exposes thrust belts that record both in-sequence and, less frequently, out-of-sequence propagation of deformation over million to millennial and decadal time scales (Figure 1). Detailed geochronologic, thermochronologic, geomorphologic, and thermobarometric studies in different parts of the Himalayan Orogen have highlighted differences in the structural style, spatiotemporal development of the structures, and effects of Cenozoic Himalayan metamorphism on the subducting Indian plate (1, and references therein). The Himalaya is tectonostratigraphically subdivided into four zones (Tethys-, Greater-, Lesser-, and Sub-Himalaya), bounded by southward-younging thrusts originating from the sole thrust known as the Main Himalayan thrust (MHT). However, studies in the Northwestern Himalaya have suggested that deformation switched back to the hinterland, resulting in the formation of out-of-sequence thrusts, reactivation of older thrusts, and zones of high seismicity and exhumation driven by tectonic and climatic processes [2-4].The Himalaya can
{"title":"Late Oligocene to Early Pliocene Exhumation and Structural Development in the Western Himalaya, Northern Pakistan: Implications for the Cenozoic Metamorphic Overprint","authors":"Irum Irum, Humaad Ghani, Edward R. Sobel, Gerold Zeilinger, Uwe Altenberger","doi":"10.2113/2024/3252550","DOIUrl":"https://doi.org/10.2113/2024/3252550","url":null,"abstract":"New middle Miocene to Pliocene (~14–3 Ma) apatite fission track (AFT) cooling ages combined with published K–Ar/Ar–Ar and zircon fission track (ZFT) ages from the Hazara and Swat regions of Pakistan are used to explain the Oligocene to Pliocene structural evolution in the Western Himalaya. The structural model explains the distribution of K–Ar/Ar–Ar ages in three distinct age groups (Proterozoic, Paleozoic-Mesozoic, and Eocene to Oligocene). The Proterozoic to Mesozoic sequence of northern Hazara and Swat experienced elevated temperature and pressure conditions, evident by reset Eocene to Oligocene K–Ar/Ar–Ar hornblende and Eocene to Miocene muscovite ages, caused by Kohistan overthrusting the Indian margin during and after the India–Asia collision. Samples from the Indus syntaxis with Paleo to Mesoproterozoic K–Ar/Ar–Ar hornblende ages and Eocene to Oligocene Ar–Ar muscovite ages show no signs of Cenozoic metamorphism; these samples were thermally imprinted up to the Ar–Ar muscovite closure temperature. Neoproterozoic to Lower Paleozoic rocks from the southern parts of Hazara and Swat show Mesozoic to Oligocene partially reset Ar–Ar muscovite ages and preservation of Ordovician metamorphism. The combined analysis of published K–Ar/Ar–Ar (muscovite), ZFT, and new AFT ages (~14–12 Ma) suggests that the Main Central thrust/Panjal thrust was active from Oligocene to early Miocene (~30–18 Ma), and the Nathia-Gali and Main Boundary thrusts were active from the middle to late Miocene (~14–9 Ma) in the Hazara area. New and published AFT ages (~6–3 Ma) from the Indus syntaxis suggest that early Pliocene tectonic thickening in the hinterland formed the N–S trending Indus anticline, creating an erosional half window in the Main Mantle thrust, forming the Indus syntaxis, and dividing the Main Central thrust sheet into the Hazara and Swat segments.The Himalaya, one of the most tectonically active mountain ranges in the world, exposes thrust belts that record both in-sequence and, less frequently, out-of-sequence propagation of deformation over million to millennial and decadal time scales (Figure 1). Detailed geochronologic, thermochronologic, geomorphologic, and thermobarometric studies in different parts of the Himalayan Orogen have highlighted differences in the structural style, spatiotemporal development of the structures, and effects of Cenozoic Himalayan metamorphism on the subducting Indian plate (1, and references therein). The Himalaya is tectonostratigraphically subdivided into four zones (Tethys-, Greater-, Lesser-, and Sub-Himalaya), bounded by southward-younging thrusts originating from the sole thrust known as the Main Himalayan thrust (MHT). However, studies in the Northwestern Himalaya have suggested that deformation switched back to the hinterland, resulting in the formation of out-of-sequence thrusts, reactivation of older thrusts, and zones of high seismicity and exhumation driven by tectonic and climatic processes [2-4].The Himalaya can ","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"9 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139509447","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-12DOI: 10.2113/2024/lithosphere_2023_225
Jens-Erik Lundstern, Theresa M. Schwartz, Cameron M. Mercer, Joseph P. Colgan, Jeremiah B. Workman, Leah E. Morgan
The cause of the transition from Mesozoic and early Cenozoic crustal shortening to later extension in the western United States is debated. In many parts of the extant Sevier hinterland, now the Basin and Range Province, the sedimentary sections that provide the most direct record of that transition remain poorly studied and lack meaningful age control. In this paper, we present field characterization supported by U-Pb detrital zircon and 40Ar/39Ar feldspar ages for ten sections across southern Nevada. We describe a newly identified basin, here named the Fallout Hills basin, which preserves >1.0 km of sedimentary deposits as old as middle Eocene, ca. 48 Ma. Deposition occurred during the 20 m.y. (million years) before the 27.60 ± 0.03 Ma Monotony Tuff blanketed much of south-central Nevada, based on 47.6 Ma and younger detrital zircon maximum depositional ages (MDAs) from near the Pintwater and Spotted Ranges. Elsewhere in southern Nevada, prevolcanic Cenozoic strata commonly form thinner (~100 m), isolated exposures that yield detrital zircon MDAs ≤10 m.y. older than (and in some cases essentially the same age as) the ca. 27–28 Ma ignimbrites that cap the sections. A variable but overall upward-fining facies pattern is observed in both the Fallout Hills basin and the thinner sections. These localized patterns imply topographic changes that are unlikely to reflect plate-scale processes and are not consistent with large-magnitude extension. Instead, variable uplift due to magmatism combined with antecedent topographic relief from thrust faulting and subsequent erosion likely provided accommodation for these deposits.Supracrustal rocks often provide some of the only records of topographic evolution and magmatic activity in ancient orogenic systems. They are, therefore, valuable for inferring the geometry, timing, and causal factors of tectonism and for constraining topographic change for use in geodynamic models [1, 2]. There is active debate concerning the fundamental transition that occurred in the western United States (Figure 1) from Mesozoic and early Cenozoic crustal shortening to Neogene basin-and-range extension [3, 4], which has implications for the study of crustal dynamics worldwide, including the stability of compressional orogens and the causes of extension. Sedimentary rocks deposited during this transition are sparse and generally not well studied across Nevada, eastern California, and western Utah, where one model has proposed that Cretaceous shortening thickened the crust sufficiently to support an orogenic highland commonly referred to as the Nevadaplano [5], while another has suggested that elevated topography was achieved only later due to south-migrating middle Cenozoic volcanism [3, 6]. Detailed constraints on the timing and setting of deposition would be valuable for understanding surface dynamics and the associated driving forces during this time and would assist with testing between sharply differing models that have been p
{"title":"Paleogene Sedimentary Basin Development in Southern Nevada, USA","authors":"Jens-Erik Lundstern, Theresa M. Schwartz, Cameron M. Mercer, Joseph P. Colgan, Jeremiah B. Workman, Leah E. Morgan","doi":"10.2113/2024/lithosphere_2023_225","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_225","url":null,"abstract":"The cause of the transition from Mesozoic and early Cenozoic crustal shortening to later extension in the western United States is debated. In many parts of the extant Sevier hinterland, now the Basin and Range Province, the sedimentary sections that provide the most direct record of that transition remain poorly studied and lack meaningful age control. In this paper, we present field characterization supported by U-Pb detrital zircon and 40Ar/39Ar feldspar ages for ten sections across southern Nevada. We describe a newly identified basin, here named the Fallout Hills basin, which preserves >1.0 km of sedimentary deposits as old as middle Eocene, ca. 48 Ma. Deposition occurred during the 20 m.y. (million years) before the 27.60 ± 0.03 Ma Monotony Tuff blanketed much of south-central Nevada, based on 47.6 Ma and younger detrital zircon maximum depositional ages (MDAs) from near the Pintwater and Spotted Ranges. Elsewhere in southern Nevada, prevolcanic Cenozoic strata commonly form thinner (~100 m), isolated exposures that yield detrital zircon MDAs ≤10 m.y. older than (and in some cases essentially the same age as) the ca. 27–28 Ma ignimbrites that cap the sections. A variable but overall upward-fining facies pattern is observed in both the Fallout Hills basin and the thinner sections. These localized patterns imply topographic changes that are unlikely to reflect plate-scale processes and are not consistent with large-magnitude extension. Instead, variable uplift due to magmatism combined with antecedent topographic relief from thrust faulting and subsequent erosion likely provided accommodation for these deposits.Supracrustal rocks often provide some of the only records of topographic evolution and magmatic activity in ancient orogenic systems. They are, therefore, valuable for inferring the geometry, timing, and causal factors of tectonism and for constraining topographic change for use in geodynamic models [1, 2]. There is active debate concerning the fundamental transition that occurred in the western United States (Figure 1) from Mesozoic and early Cenozoic crustal shortening to Neogene basin-and-range extension [3, 4], which has implications for the study of crustal dynamics worldwide, including the stability of compressional orogens and the causes of extension. Sedimentary rocks deposited during this transition are sparse and generally not well studied across Nevada, eastern California, and western Utah, where one model has proposed that Cretaceous shortening thickened the crust sufficiently to support an orogenic highland commonly referred to as the Nevadaplano [5], while another has suggested that elevated topography was achieved only later due to south-migrating middle Cenozoic volcanism [3, 6]. Detailed constraints on the timing and setting of deposition would be valuable for understanding surface dynamics and the associated driving forces during this time and would assist with testing between sharply differing models that have been p","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"42 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140323592","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-12DOI: 10.2113/2024/lithosphere_2023_314
Jiancheng Huang, Yong Luo, Chengzhi Pu, Song Luo, Xuefeng Si
Engineering rock containing flaws or defects under a large water source is frequently subject to the couple influence of constant crack water pressure and geostress. To investigate the fracture behavior of precracked rock under hydromechanical coupling with constant crack water pressure, compression tests were conducted on red sandstone specimens containing a single crack of different angles using a device to realize the constant crack water pressure during loading, and the failure process of rock specimens was monitored by acoustic emission (AE) technique. The results show that the presence of constant crack water pressure has a significant promotion effect on the development of shear wing cracks, and the promotion effect is influenced by the prefabricated crack angle and water pressure. As the constant crack water pressure increases, the failure mode of the 0° precrack specimen changes from “X”- shear failure to the single oblique shear failure along the shear wing crack direction, the main failure crack of the inclined precracked specimens (precrack angles of 15°, 45°, and 60°) changes from a small acute angle with the prefabricated crack to a direction along the shear wing crack, and irregular cracks occur at the chipped prefabricated crack in the 90° precracked specimen. With an increase in the constant crack water pressure, the average energy for a single hit, cumulative AE energy, and cumulative AE hits decrease, and the proportion of the tensile cracks increases and that of the shear cracks decreases.In underground mining, water conservancy and hydropower, geothermal development, and oil exploitation projects, rock structure inevitably contains various flaws and can be damaged and destroyed due to stress variations [1-7]. Therefore, the study of the failure characteristics of rocks with original crack, such as the crack propagation mechanism [8-11], mechanical properties [12-14], and acoustic emission (AE) characteristics [15-17], has been popular in recent years. Water, as a common liquid in the earth crust, is commonly present in rock flaws in underground engineering structures [18]. Due to the low permeability, rocks are often subjected to the influence of crack water pressure. In general, there are two common types of crack water pressure in rocks, as demonstrated by cases I and II in Figure 1. In case I, the crack water is not connected to a large water source, and the crack water pressure is not replenished in time during crack expansion. Therefore, the crack water pressure decreases as the crack expands. In case II, the crack water is connected to a large water source, the crack water pressure is immediately replenished during the crack propagation, so that the water pressure remains almost constant. This type of crack water pressure is termed the constant crack water pressure. With the rapid development of various types of rock engineering, increasing underground projects are being constructed under large water sources (e.g., tunn
大水源下含有缺陷或瑕疵的工程岩石经常受到恒定裂隙水压力和地应力的耦合影响。为了研究在恒定裂隙水压力的水力机械耦合作用下预裂隙岩石的断裂行为，利用加载过程中实现恒定裂隙水压力的装置，对含有不同角度单裂隙的红砂岩试件进行了压缩试验，并利用声发射（AE）技术监测了岩石试件的破坏过程。结果表明，恒定裂缝水压的存在对剪切翼裂缝的发展有显著的促进作用，而促进作用受预制裂缝角度和水压的影响。随着恒定裂缝水压的增加，0° 预裂缝试样的破坏模式由 "X "型剪切破坏转变为沿剪切翼裂缝方向的单斜剪切破坏，倾斜预裂缝试样（预裂缝角度为 15°、45° 和 60°）的主要破坏裂缝由与预制裂缝成小锐角转变为沿剪切翼裂缝方向，90° 预裂缝试样的崩裂预制裂缝处出现不规则裂缝。在地下采矿、水利水电、地热开发、石油开采等工程中，岩石结构不可避免地存在各种缺陷，会因应力变化而受到破坏和破坏[1-7]。因此，对带有原始裂缝的岩石的破坏特征，如裂缝扩展机理[8-11]、力学性能[12-14]和声发射（AE）特征[15-17]等的研究近年来很受欢迎。水作为地壳中常见的液体，通常存在于地下工程结构的岩石缺陷中[18]。由于渗透率低，岩石经常受到裂隙水压力的影响。一般来说，岩石中常见的裂隙水压力有两种类型，如图 1 中的情况 I 和情况 II 所示。在情况 I 中，裂隙水没有与大水源相连，裂隙水压力在裂隙扩展过程中得不到及时补充。因此，裂缝水压会随着裂缝的扩展而降低。在情况 II 中，裂缝水与大型水源相连，裂缝水压在裂缝扩展过程中立即得到补充，因此水压几乎保持恒定。这种裂缝水压称为恒定裂缝水压。随着各类岩石工程的快速发展，越来越多的地下工程在大型水源下施工（如湖底隧道和海底采矿）。遇到恒定裂隙水压力的情况也越来越多。因此，有必要研究恒定裂隙水压力对裂隙岩石破坏行为的影响。目前，已有大量关于裂隙水压力对岩石破坏特性影响的数值和实验研究[19-25]。Pu 等[26]利用数值模拟方法研究了裂隙水压力对裂隙扩展和岩石强度的影响，揭示了水压力作用下岩石的裂隙破坏和断裂机理。Li 等[27]利用三维数值模型中的快速拉格朗日连续体分析方法研究了裂隙水压力作用下单轴压缩岩石的破坏演化过程。Wang 等[28]提出了一种利用扩展有限元法模拟渗流应力耦合作用下裂缝扩展的数值方法。Li 等[29]提出了一种基于均质化方法和水平集方法的岩石异质性和多水力裂缝扩展建模方法。Ma 等[30]通过数值和分析方法分析了压裂液热物理参数对干热岩破坏的影响。Haeri 等人[31] 利用断裂分析代码模拟了岩石中节理分布对圆孔水力压裂的影响。Gu 等人[32-34]通过实验方法研究了孔隙度对水饱和砂岩和煤动态响应的影响。他们发现水饱和砂岩和煤的削弱程度与孔隙度呈正相关。他们还探讨了孔隙度和含水率对软煤断裂扩展和动态强度的影响机理。Li 等人
{"title":"Compressive Fracture Behavior and Acoustic Emission Characteristics of Sandstone under Constant Crack Water Pressure","authors":"Jiancheng Huang, Yong Luo, Chengzhi Pu, Song Luo, Xuefeng Si","doi":"10.2113/2024/lithosphere_2023_314","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_314","url":null,"abstract":"Engineering rock containing flaws or defects under a large water source is frequently subject to the couple influence of constant crack water pressure and geostress. To investigate the fracture behavior of precracked rock under hydromechanical coupling with constant crack water pressure, compression tests were conducted on red sandstone specimens containing a single crack of different angles using a device to realize the constant crack water pressure during loading, and the failure process of rock specimens was monitored by acoustic emission (AE) technique. The results show that the presence of constant crack water pressure has a significant promotion effect on the development of shear wing cracks, and the promotion effect is influenced by the prefabricated crack angle and water pressure. As the constant crack water pressure increases, the failure mode of the 0° precrack specimen changes from “X”- shear failure to the single oblique shear failure along the shear wing crack direction, the main failure crack of the inclined precracked specimens (precrack angles of 15°, 45°, and 60°) changes from a small acute angle with the prefabricated crack to a direction along the shear wing crack, and irregular cracks occur at the chipped prefabricated crack in the 90° precracked specimen. With an increase in the constant crack water pressure, the average energy for a single hit, cumulative AE energy, and cumulative AE hits decrease, and the proportion of the tensile cracks increases and that of the shear cracks decreases.In underground mining, water conservancy and hydropower, geothermal development, and oil exploitation projects, rock structure inevitably contains various flaws and can be damaged and destroyed due to stress variations [1-7]. Therefore, the study of the failure characteristics of rocks with original crack, such as the crack propagation mechanism [8-11], mechanical properties [12-14], and acoustic emission (AE) characteristics [15-17], has been popular in recent years. Water, as a common liquid in the earth crust, is commonly present in rock flaws in underground engineering structures [18]. Due to the low permeability, rocks are often subjected to the influence of crack water pressure. In general, there are two common types of crack water pressure in rocks, as demonstrated by cases I and II in Figure 1. In case I, the crack water is not connected to a large water source, and the crack water pressure is not replenished in time during crack expansion. Therefore, the crack water pressure decreases as the crack expands. In case II, the crack water is connected to a large water source, the crack water pressure is immediately replenished during the crack propagation, so that the water pressure remains almost constant. This type of crack water pressure is termed the constant crack water pressure. With the rapid development of various types of rock engineering, increasing underground projects are being constructed under large water sources (e.g., tunn","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"40 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139772995","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-12DOI: 10.2113/2024/lithosphere_2023_273
Baoyi Zhang, Zhanghao Xu, Xiuzong Wei, Lei Song, Syed Yasir Ali Shah, Umair Khan, Linze Du, Xuefeng Li
Lithostratigraphic modeling holds a vital role in mineral resource exploration and geological studies. In this study, we introduce a novel approach for automating pseudo-lithostratigraphic modeling in the deep subsurface, leveraging inversed geophysical properties. We propose a three-dimensional convolutional neural network with adaptive moment estimation (3D Adam-CNN) to achieve this objective. Our model employs 3D geophysical properties as input features for training, concurrently reconstructing a 3D geological model of the shallow subsurface for lithostratigraphic labeling purposes. To enhance the accuracy of pseudo-lithostratigraphic modeling during the model training phase, we redesign the 3D CNN framework, fine-tuning its parameters using the Adam optimizer. The Adam optimizer ensures controlled parameter updates with minimal memory overhead, rendering it particularly well-suited for convolutional learning involving huge 3D datasets with multi-dimensional features. To validate our proposed 3D Adam-CNN model, we compare the performance of our approach with 1D and 2D CNN models in the Qingniandian area of Heilongjiang Province, Northeastern China. By cross-matching the model’s predictions with manually modeled shallow subsurface lithostratigraphic distributions, we substantiate its reliability and accuracy. The 3D Adam-CNN model emerges as a robust and effective solution for lithostratigraphic modeling in the deep subsurface, utilizing geophysical properties.Litho-strata manifest a broad range of rock properties arising from distinct geological processes, for example, weathering, compaction, metamorphism, and deformation. These intricate processes, when combined, yield complex representations of various litho-strata. Furthermore, lithostratigraphy dictates the physical and chemical attributes of the litho-strata, the distribution of which is intimately intertwined with mineral resource distribution. Traditional lithostratigraphic identification methods, for example, borehole drilling and trenching, necessitate manual interpretation of field-collected or borehole core samples. While direct, these methods prove costly, time-consuming, and inadequate for identifying deep subsurface litho-strata in a large area. Additionally, human subjectivity and experience wield considerable influence over these conventional approaches’ outcomes. Hence, there exists a need for more reliable lithostratigraphic identification methods using physical or chemical properties. Three-dimensional geological modeling plays a vital role in portraying subsurface spatial characteristics, for example, litho-strata, fault networks, physical and chemical properties, and quantitative mineralization [1-3]. With the advancements in deep-penetration geophysical and geochemical exploration, the prospect of studying geological bodies’ physical and chemical properties from a 3D perspective becomes feasible [4-6]. These methodologies deepen the comprehension of the lithostratigraphy’
{"title":"Deep Subsurface Pseudo-Lithostratigraphic Modeling Based on Three-Dimensional Convolutional Neural Network (3D CNN) Using Inversed Geophysical Properties and Shallow Subsurface Geological Model","authors":"Baoyi Zhang, Zhanghao Xu, Xiuzong Wei, Lei Song, Syed Yasir Ali Shah, Umair Khan, Linze Du, Xuefeng Li","doi":"10.2113/2024/lithosphere_2023_273","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_273","url":null,"abstract":"Lithostratigraphic modeling holds a vital role in mineral resource exploration and geological studies. In this study, we introduce a novel approach for automating pseudo-lithostratigraphic modeling in the deep subsurface, leveraging inversed geophysical properties. We propose a three-dimensional convolutional neural network with adaptive moment estimation (3D Adam-CNN) to achieve this objective. Our model employs 3D geophysical properties as input features for training, concurrently reconstructing a 3D geological model of the shallow subsurface for lithostratigraphic labeling purposes. To enhance the accuracy of pseudo-lithostratigraphic modeling during the model training phase, we redesign the 3D CNN framework, fine-tuning its parameters using the Adam optimizer. The Adam optimizer ensures controlled parameter updates with minimal memory overhead, rendering it particularly well-suited for convolutional learning involving huge 3D datasets with multi-dimensional features. To validate our proposed 3D Adam-CNN model, we compare the performance of our approach with 1D and 2D CNN models in the Qingniandian area of Heilongjiang Province, Northeastern China. By cross-matching the model’s predictions with manually modeled shallow subsurface lithostratigraphic distributions, we substantiate its reliability and accuracy. The 3D Adam-CNN model emerges as a robust and effective solution for lithostratigraphic modeling in the deep subsurface, utilizing geophysical properties.Litho-strata manifest a broad range of rock properties arising from distinct geological processes, for example, weathering, compaction, metamorphism, and deformation. These intricate processes, when combined, yield complex representations of various litho-strata. Furthermore, lithostratigraphy dictates the physical and chemical attributes of the litho-strata, the distribution of which is intimately intertwined with mineral resource distribution. Traditional lithostratigraphic identification methods, for example, borehole drilling and trenching, necessitate manual interpretation of field-collected or borehole core samples. While direct, these methods prove costly, time-consuming, and inadequate for identifying deep subsurface litho-strata in a large area. Additionally, human subjectivity and experience wield considerable influence over these conventional approaches’ outcomes. Hence, there exists a need for more reliable lithostratigraphic identification methods using physical or chemical properties. Three-dimensional geological modeling plays a vital role in portraying subsurface spatial characteristics, for example, litho-strata, fault networks, physical and chemical properties, and quantitative mineralization [1-3]. With the advancements in deep-penetration geophysical and geochemical exploration, the prospect of studying geological bodies’ physical and chemical properties from a 3D perspective becomes feasible [4-6]. These methodologies deepen the comprehension of the lithostratigraphy’","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"22 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139759022","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To constrain the late Triassic tectonic evolution of the Songpan-Ganzi orogenic belt, we present new whole-rock and in situ apatite geochemistry for plutonic rocks in its eastern margin. The Taiyanghe pluton can be classified into two rock types: dioritic and granitic rocks. The former exhibits low SiO2 and MgO contents but high Al2O3, Th, LREE contents, and Th/Yb and Th/Nb ratios, as well as low Ba/La and Ba/Th ratios and enriched Sr-Nd isotopic compositions, which, together with apatite geochemistry and Nd isotopes, indicate that they were derived from low degrees of partial melting of lithospheric mantle metasomatized by sediment-derived melts. The latter is characterized by high Sr and low Y and Yb, with elevated Sr/Y and (La/Yb)N ratios, implying an adakitic affinity. Notably, their similar Sr-Nd isotopic compositions indicate an origin from partial melts of a newly underplated lower crust. The Maoergai granitic rocks, characterized by high Sr and low Y and Yb contents with high Sr/Y and (La/Yb)N ratios, are indicative of adakitic rocks. In combination with the enriched whole-rock Sr-Nd isotopes and the apatite Nd isotopic data, we suggest that they were generated by the partial melting of the ancient thickened mafic lower crust. The Markam and Yanggonghai felsic granitoid rocks are peraluminous and similar to typical S-type granitoids, indicating an origin from remelting of the Triassic metasedimentary rocks. Based on the temporal-spatial relationship of the late Triassic plutonic rocks in the orogenic belt, we suggest that these rocks were formed in association with the roll-back and subsequent break-off of a subducted slab of the Paleo-Tethys Ocean. During the subduction, the formation of the Maoergai adakitic rocks was triggered by slab roll-back, whereas the magmatic “flare up” (ca. 216–200 Ma) was likely caused by slab break-off. This indicates that the final closure of the Paleo-Tethys Ocean happened in the end of the Triassic or Early Jurassic.Orogenic belts are important sites where voluminous magmatic rocks with diverse lithologic and geochemical characteristics are produced [1-3]. However, the diversity of magmatic rocks developed in orogenic belts has been a topic of debate concerning their sources, magmatic processes, and geodynamic settings involved in petrogenesis [1-7]. Particular attention has been usually focused on the geodynamic framework, which can be generally regarded to be grouped into two types according to the temporal relationship to the tectonic evolutionary process of orogenic belts: subduction and postcollision [4, 8]. Magmatic rocks with diverse geochemical characteristics in orogenic belts offer a critical window to understand the tectonic evolution of these stages [1, 3, 4, 7]. Therefore, the tectonic evolution of orogenic belts could be accurately reconstructed by investigating the temporal-spatial variability and geochemical signatures of these diverse magmatic rocks.The Songpan-Ganzi orogenic belt is widel
{"title":"Whole-Rock and Apatite Geochemistry of Late Triassic Plutonic Rocks in the Eastern Songpan-Ganzi Orogenic Belt: Petrogenesis and Implications for Tectonic Evolution","authors":"Haoyu Yan, Zhiqin Xu, Guangwei Li, Bihai Zheng, Jianguo Gao, Xiaoping Long","doi":"10.2113/2024/lithosphere_2023_284","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_284","url":null,"abstract":"To constrain the late Triassic tectonic evolution of the Songpan-Ganzi orogenic belt, we present new whole-rock and in situ apatite geochemistry for plutonic rocks in its eastern margin. The Taiyanghe pluton can be classified into two rock types: dioritic and granitic rocks. The former exhibits low SiO2 and MgO contents but high Al2O3, Th, LREE contents, and Th/Yb and Th/Nb ratios, as well as low Ba/La and Ba/Th ratios and enriched Sr-Nd isotopic compositions, which, together with apatite geochemistry and Nd isotopes, indicate that they were derived from low degrees of partial melting of lithospheric mantle metasomatized by sediment-derived melts. The latter is characterized by high Sr and low Y and Yb, with elevated Sr/Y and (La/Yb)N ratios, implying an adakitic affinity. Notably, their similar Sr-Nd isotopic compositions indicate an origin from partial melts of a newly underplated lower crust. The Maoergai granitic rocks, characterized by high Sr and low Y and Yb contents with high Sr/Y and (La/Yb)N ratios, are indicative of adakitic rocks. In combination with the enriched whole-rock Sr-Nd isotopes and the apatite Nd isotopic data, we suggest that they were generated by the partial melting of the ancient thickened mafic lower crust. The Markam and Yanggonghai felsic granitoid rocks are peraluminous and similar to typical S-type granitoids, indicating an origin from remelting of the Triassic metasedimentary rocks. Based on the temporal-spatial relationship of the late Triassic plutonic rocks in the orogenic belt, we suggest that these rocks were formed in association with the roll-back and subsequent break-off of a subducted slab of the Paleo-Tethys Ocean. During the subduction, the formation of the Maoergai adakitic rocks was triggered by slab roll-back, whereas the magmatic “flare up” (ca. 216–200 Ma) was likely caused by slab break-off. This indicates that the final closure of the Paleo-Tethys Ocean happened in the end of the Triassic or Early Jurassic.Orogenic belts are important sites where voluminous magmatic rocks with diverse lithologic and geochemical characteristics are produced [1-3]. However, the diversity of magmatic rocks developed in orogenic belts has been a topic of debate concerning their sources, magmatic processes, and geodynamic settings involved in petrogenesis [1-7]. Particular attention has been usually focused on the geodynamic framework, which can be generally regarded to be grouped into two types according to the temporal relationship to the tectonic evolutionary process of orogenic belts: subduction and postcollision [4, 8]. Magmatic rocks with diverse geochemical characteristics in orogenic belts offer a critical window to understand the tectonic evolution of these stages [1, 3, 4, 7]. Therefore, the tectonic evolution of orogenic belts could be accurately reconstructed by investigating the temporal-spatial variability and geochemical signatures of these diverse magmatic rocks.The Songpan-Ganzi orogenic belt is widel","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"235 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139465083","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：